Indeed. But whether rendered as "far London" or "fair London", it is just a bit of phatic poeticising. Islington is a borough pretty well adjacent to the City at its southern extremity. From Angel Station walk straight due south down Goswell Road and Aldersgate Street and you'll come to St Paul's in, maybe, ¾-mile. Still, as pointed out above, couples can be parted socially by more than mere distance.

And as to that "confidently asserted"; as Steve points out, Roy carefully avoided saying by whom!

~M~